1. Field of the Invention
The present invention relates to a probe capable of picking up an electric signal from a circuit component such as a chip mounted on a printed wiring board.
2. Description of the Prior Art
Inspection of a circuit component such as a chip or a mounting device, in general, requires an inspection apparatus such as an oscilloscope, a voltammeter, a logic analyzer, and the like. Such an inspection apparatus is designed to analyze an electric signal in the circuit component for detecting the waveform and/or voltage and current values of the electric signal. A probe is employed to pick up the electric signal from the circuit component.
A probe comprises in general an insulated grip and a detect contact attached at the tip end of the insulated grip. If the detect contact comprises a clamp or hook member of metallic material, the detect contact can clamp or hook around a lead wire extending out from a circuit component. In this way, the tip end of the probe can be temporarily fixed at the lead wire. In addition, if the detect contact is formed into a metallic pipe embedded in the tip end of the probe, the detect contact can receive the insertion of a terminal pin provided on a circuit component. Thus, the tip end of the probe can be temporarily fixed at the terminal pin.
For example, a circuit component such as a ball grid array (BGA) comprises solder bumps. The solder bumps are arranged in a grid pattern on an underneath surface which is opposed to a printed surface of the printed wiring board. No lead wire or terminal pin is exposed out of the circuit component. Moreover, once the circuit component has been mounted on the printed wiring board, the solder bumps are hidden underneath the circuit component, so that the aforementioned probe cannot even reach the solder bumps.
Under the above circumstance, one inspection method is proposed to pick up an electric signal from wires printed on the surface of the printed wiring board around the circuit component, since the printed wires expand around the circuit component. However, this method requires identifying the circuit pattern on the printed wiring board prior to actual inspection. It is troublesome.
It is accordingly an object of the present invention to provide a probe capable of easily picking up an electric signal from a solder bump.
According to a first aspect of the present invention, there is provided a probe comprising: a grip body attached with an electric terminal; an arm body extending from the grip body; a contact electrode formed on the arm body at its side face; and a wire electrically connecting the contact electrode with the electric terminal.
The probe can be inserted between a printed wiring board and a circuit component which has been mounted on the printed wiring board, for example. When the arm body is slid along the surface of the printed wiring board underneath the circuit component, the contact electrode may contact a solder bump standing on the surface of the printed wiring board. The length of the arm body may serve to protrude the grip body of the probe from the outer periphery of the circuit component, so that it is possible to easily pick up an electric signal at the solder bump with the electric terminal formed on the grip body. An electric signal at the contact electrode is transmitted to the electric terminal via the wire.
The width of the arm body is preferably set smaller than an interval between solder bumps arranged on an underneath surface of a circuit component. Such width may contribute to a smooth insertion of the arm body between the solder bumps without any resistance from the solder bumps.
In addition, the length of the arm body is preferably set longer than a distance between an outer periphery of a circuit component and a solder bump arranged on an underneath surface of the circuit component. Such length may serve to leave the electric terminal on the grip body outside the outer periphery of the circuit component when the contact electrode reaches the target solder bump.
A protrusion may be formed on the arm body to extend in a direction opposite to a vertical vector imaginatively established on the surface of the contact electrode. Such protrusion may serve to position the contact electrode with respect to the target solder bump by contacting the solder bump opposed to the target solder bump.
According to a second aspect of the present invention, there is provided a probe comprising: a grip body attached with a plurality of electric terminals; an arm body extending from the grip body; a plurality of contact electrodes formed on the arm body at its side face; and a plurality of wires electrically connecting the respective contact electrodes with the corresponding electric terminals.
With the above probe, a plurality of contact electrodes formed on the arm body enable detection of electric signals at a plurality of solder bumps, for example, at the same time with the single arm body. In this case, the contact electrodes may be formed at a side surface of the arm body, or a pair of side surfaces of the arm body. In addition, a plurality of arm bodies may be formed for the single grip body.
In the above probe, an interval between the contact electrodes is preferably set at an interval between solder bumps arranged on a coupling surface of a circuit component. The set interval may serve to contact at least a pair of the contact electrodes with the corresponding pair of the solder bumps. The interval may be set dependent of the interval between the target solder bumps.
The arm body may comprise an insulation layer for isolating the respective wires. Employment of layered structure with the insulation layer may serve to incorporate a plurality of independent wires in a body of the probe without contact between the independent wires. Short can reliably be prevented. The layered structure can be obtained with a conventional layering technique.
Furthermore, according to a third aspect of the present invention, there is provided an inspection apparatus comprising: a main system capable of analyzing an electric signal; and a probe with a contact electrode formed on a side surface of an arm body extending from a grip body so as to supply the main system with an electric signal detected at the contact electrode.
The aforementioned probes according to the first and second aspects of the present invention may be connected to the main system. Accordingly, insertion of the arm body between a printed wiring board and a mounted circuit component enables easier detection of an electric signal at a solder bump arranged between the printed wiring board and the mounted circuit component. The probe may comprise a plurality of the contact electrodes. The main system may be any of an oscilloscope, a voltmeter, an ammeter, and a logic analyzer.